Abstract

The purpose of this paper is to seek a way to improve the transfer of post crack forces in concrete using fibre technology. When straight fibres are added to a concrete mix, the direction of the fibres can be influenced by the mould, balling together and random orientation. This may result in a smaller percentage of fibres being effective when compared to that which it was originally designed for, when coping with post crack forces in concrete. The closed loop fibre technology is designed to place the fibres in an orientation and position where they will be of most benefit, thus reducing the likelihood of having fibres in concrete where they will not be of structural benefit and as a result of this, they will maximise the engineering qualities of the fibre addition.

Beams were manufactured with a fixed addition of fibres by weight, and then they were tested for toughness (energy absorption) using a three point test, recording load and deflection. As an additional measure of the beams ability to absorb energy, a drop hammer test was used to analyse the energy absorbed and the total impact energy dissipated. The findings showed a significant improvement in performance when closed loop fibres were used, when compared to an equal dose of straight steel fibres.

This work is significant in that the closed loop fibres are not commercially available at this present time and this research assists in a new product development. Closed loop fibres use lower amounts of steel than straight fibres for an equivalent performance to be achieved. They therefore have sustainability credentials with regard to carbon footprint and use of raw materials in construction and building.